How do i change value of players cash only if player have a key in hes inventory?

Here is my script. It works like this but i don't want other players to be able to click and get money if they don't have a key.

key is called "Blue Master Key" and it is a tool that player holds in hes inventory.

function onClicked()
for i=1, 1 do
    for _, player in ipairs(game.Players:GetPlayers()) do
        if player:FindFirstChild("Xp") then
            player.Cash.Cash.Value = player.Cash.Cash.Value + 2000
        end
    end
end
end
script.Parent.ClickDetector.MouseClick:connect(onClicked)

Ok so, since you want to see if they have the key in their backpack, were are gonna use the argument that is passed when the MouseClick event is fired.

Here is what I mean :

part.ClickDetector.MouseClick:Connect(function(playerWhoClicked) --It gives us the player who clicked here
	print(playerWhoClicked)
end)

Since we can get the player like this, we can then access their backpack and see whether they have the key or not.

function onClicked(playerWhoClicked)
	local player = playerWhoClicked --Storing the player
	local backpack = player.Backpack -- Their Backpack
	if backpack:FindFirstChild('Blue Master Key') then -- looks for the key
		--Since its found the key, it can do the next bit
		if player:FindFirstChild("Xp") then 
	            player.Cash.Cash.Value = player.Cash.Cash.Value + 2000
	        end
	else
		print('No key found') --No key found
	end
end
script.Parent.ClickDetector.MouseClick:Connect(onClicked)