hola, buenas tardes me podran ayudar con estos problemas del tema derivadas como razn de cambio, no me salen y estoy muy preocupada por que no les entiendo, en la imagen estn las respuestas que vienen en mi libro

" Derived as a reason for change " 2. Filling a rectangular cistern 4 m 3 m " ) water enters a cistern at a rate of 0.5 m3 / min. How fast does the water level rise If the base of the cistern is a 3 X3 meter rectangle? The answer should come out = 40.042 m / min. dh 3 - Electricity d+ 2. The equivalent electrical resistance ( R) with R 1 and R2 connected in parallel , is given by: 1 = R R 1 R 2 where R, B1 and Bz are measured in Ohms , By and R2 are growing at the rate of 1.5 and 2 Ohms per second, respectively, at what rate is A changing when RJ = 401 and R2 = 501 dR Solution :a+ 0. 86 this a a R 1 5 R2 E B b