What formula is used?

A bank expects to raise $37 million in new money if it pays a deposit rate of 6%,$91 million in new money if it pays a deposit rate of 10%, and it can raise $113 million in new money if it pays a deposit rate of 13%. The bank expects to earn 9.5% on all money that it receives in new deposits. What is the marginal cost of deposits if this bank raises its deposit rate from 10% to 13%? *Please type your answer as percentage and not as decimal (i.e. 5.2 and not 0.052). Do not type the \% symbol