Art of Electronics, 3rd Ed, pg. 164-165 give an example of naively using a 4000-series CMOS logic gate to directly switch a power MOSFET, disregarding the significant gate current required to charge the MOSFET capacitance. They give the following values: VDD = +10V, C_mosfet = 200pF, maximum current source/sink capability of logic gate = +/- 1mA. Their conclusion is that it will take approximately 50us to switch the MOSFET on/off. I don't see how they come up with this number. If the logic gate is slew-rate limited, then it will take t = CV/I = (200pF)(10V)/1mA = 2us to turn on the MOSFET.
I checked the second edition and although they use different numbers, I'm still not able to come up with the provided answer. What am I doing wrong?