"Determine the interest rate (i) that makes the pairs of cash flows shown economically equivalent. Calculate the Present Worth of the second cash flow series at an 18% annual interest rate using only one formula and then check the answer using another method of calculation." $1380 S1380 $1380 S1380 S1380 $1380 $1380 4 Years 1=? S2500 $1875 S1406 S1055 $791 $593 445 2 4 . Years