Given a loan with principal amount, P, time, T, in years and rate, R %,
the interest I is given by
For the 4-year loan,
P = $10000, R = 4%, T = 4years
For the 6-year loan,
P = $10000, R = 5%, T = 6years,
therefore,
Hence,
the difference = $3000 - $1600 = $1400