John has just opened a savings account at sugar land united bank with a $250 deposit. he plans to deposit $50 into his savings account twice a month. which equation best represents the problem if y represents the total amount of money in his savings account and x represents the number of months John has been saving money?
a. y = 250 + 50x
b. y = 50x - 250
c. y = 100x + 250
d. y = 100x - 25