In order to compute this one you want to use the annuity formula
PMT = P * [rate(1 + rate)^n] / [(1 + rate)^n – 1]
For this loan that would be
PMT = 70000 * [0.05/12 (1 + 0.05/12)^51] / [(1 + 0.05/12)^51 – 1]
PMT = $1526.39
So the monthly payment here should be $1526.39