Select the function that represents the simple interest formula. a. a(n)=(n-1)(p*i)^n, where n is any real number b. a(n)=n+(p-1)i*p, where n is a positive integer c. a(n)=p(1+i)^n-1, where n is any real number d. a(n)=p+(n-1)i*p, where n is a positive integer