10.( 1) When 0 ≤ x ≤ 4, it looks like a straight line passing through the origin, so it is a proportional function. Let y=kx, if (4,20) is substituted into the analytical formula, and k=5, the analytical formula is y=5x.

⑵ When 4 ≤ x ≤ 12, it looks like a straight line, which can be set as y = MX+B, (4,20) and (12,30) and then substituted into the binary linear equations about m and b respectively, and the solution is m= 1.25 and b = 60.

(3) The water inflow is 5 liters/minute, which is k in (1); Effluent (5- 1.25)=3.75 l/min. M-K。