hmmm let hmm come to think..5£ is a bit too much for some junk glass anyway =) hehee, anyhow. so 5cents then
let us nevermind the price for now, and see how many grams are needed for the 6hours
so 1 bottle (500 grams), gives Adam 7.5 minutes of oven time
how many grams will it be for 6hrs or 6 * 60 = 360 minutes?

that's how many "p" (pennies? pence? pounds?) will it be for 6hrs of oven time for Adam