Pls i need this tonight dad bought $200,000 of term life insurance at the rate of $5.40 per thousand-dollar unit. how much is the annual premium?

Can someone explain to me how to do

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?

Compute the standard deviation of the following set of data to the nearest whole number. 10, 10, 15, 20, 25