Jack sees commuting by train and bus as perfect substitutes (U = B + T), that is, he would exchange 1 commute by bus for 1 commute by train. The price of a bus ticket is $1.50 and the price of a train ticket is $ 2.00. Jack has $6.00 to spend on commuting. Determine the Jack's best affordable choice? By how much can train ticket prices increase without making Jack worse off?