The discharge per second of a double acting reciprocating pump is ___________.
(A: cross-sectional area of the piston, N: crank speed (in rpm) and L: stroke (stroke, in metres)
1
\(\frac{2 A L N}{60}\)
2
\(\frac{8 A L N}{60}\)
3
\(\frac{4A L N}{60}\)
4
\(\frac{A L N}{60}\)