Jenny works at a post office she puts stamps on packages eack package needs 5 stamps how many stamps will jenny use if she is mailing 105 packages? i need the answer now plz

Dakota earned $7.50 in interest in account a and $18.75 in interest in account b after 15 months. if the simple interest rate is 4% for account a and 5% for account b, which account has the greater principal? explain. to make it a little easier, there is an image. good luck!