In a compound gear train shown in figure, the power is transmitted from a motor shaft to output shaft. The motor shaft is connected to gear 1 whereas the output shaft is connected gear 4.

The gears 2 and 3 are mounted on the same shaft. The motor shaft is rotating at 1250 rpm in the clockwise direction. Find the speed of the output shaft (in rpm) if number of teeth on gears 1 2, 3 and 4 are 30, 75, 20 and 50.