Water flows from the bottom of a storage tank at a rate of
r(t) = 300 − 6t
liters per minute, where 0 ≤ t ≤ 50. find the amount of water that flows from the tank during the first 45 minutes.

Sam opened a money-market account that pays 3% simple interest. he started the account with $7,000 and made no further deposits. when he closed the account, he had earned $420 in interest. how long did he keep his account open?