Taste-buddy

Bob is a food lover. Every day he enjoys his lunch break in his office canteen where n different food items are kept in a row. After eating the $i^{th}$ food item, Bob gets a tastiness of $a_{i}$. The lunch break lasts for $k$ minutes and it takes him exactly $t_{i}$ minutes to finish the $i^{th}$ item. Bob does his lunch in the following manner : - He chooses a particular item and starts eating