When leveled up how do I add 50 health to the max health for the player?

Okay so I have made this script for my Role playing game to make you level up when you get 50 XP, but I want the script to also increase the max health by 50 whenever the player gets 50 XP.

function onXPChanged(player, XP, level)
    if XP.Value>=level.Value * 50 then
        XP.Value = XP.Value - level.Value * 50
        level.Value = level.Value + 1
    end
end

function onLevelUp(player, XP, level)
    if player.Character~=nil then
        for i = 1,5 do
            local fireworks = Instance.new("Part")
            fireworks.Shape = 0
            fireworks.formFactor = "Symmetric"
            fireworks.Size = Vector3.new(1,1,1)
            fireworks.BrickColor = BrickColor.Random()
            fireworks.CFrame = player.Character.Head.CFrame + Vector3.new(0,2,0)
            fireworks.Parent = game.Workspace
            game:GetService("Debris"):AddItem(fireworks, 2)
            fireworks.Velocity = Vector3.new(math.random(-30,30),math.random(-30,30),math.random(-30,30))
        end
    end
    local m = Instance.new("Hint")
    m.Parent = game.Workspace
    m.Text = player.Name .. "Leveled up"
    wait(3)
    m.Parent = nil
end

function onPlayerRespawned(player)
    wait(5)
    player.Character.Humanoid.Health = player.leaderstats.Level * 100
    player.Character.Humanoid.MaxHealth = player.leaderstats.Level * 100
--[[
    local stuff = player.Backpack:GetChildren()
    wait(5)
    for i = 1,#stuff do
        local name = stuff[i].Name
        if game.Starterpack:findFirstChild(name)==nil then
            stuff[i]:Clone().Parent = player.Backpack
        end
    end
--]]
end

function onPlayerEntered(newPlayer)
    local stats = Instance.new("IntValue")
    stats.Name = "leaderstats"

    local xp = Instance.new("IntValue")
    xp.Name = "XP"
    xp.Value = 0

    local level = Instance.new("IntValue")
    level.Name = "Lvl"
    level.Value = 1

    local c = Instance.new("IntValue")
    c.Name = "Gold"
    c.Value = 0

    xp.Parent = stats
    level.Parent = stats
    c.Parent = stats

    stats.Parent = newPlayer

    xp.Changed:connect(function() onXPChanged(newPlayer, xp, level) end)
    level.Changed:connect(function() onLevelUp(newPlayer, xp, level) end)

    newPlayer.Changed:connect(function (property)
        if (property == "Character") then
            onPlayerRespawned(newPlayer)
        end
    end)
end

game.Players.ChildAdded:connect(onPlayerEntered)

Thanks if you read this and double thanks if you reply.