Using Scheme code Some credit-card companies pay back a small portion of the charges a customer makes over a year. One company returns

(a) 0.25% for the first $500 of charges,

(b) 0.50% for the next $1000 (that is, the portion between $500 and $1500),

(c) 0.75% for the next $1000 (that is, the portion between $1500 and $2500),

(d) and 1.0% for everything above $2500.

Thus, a customer who charges $400 a year receives $1.00, which is 0.25% * 400, and one who charges $1,400 a year receives $5.75, which is 1.25 = 0.25% * 500 for the first $500 and 0.50% * 900 = 4.50 for the next $900.

Define the function payback, which consumes a charge amount and computes the corresponding pay-back amount.