Alight meter reports that a camera setting of 1125s at f/4.0 will give a correct exposure. but the photographer wishes to use f/16 to increase the depth of field. what should the shutter speed be?

Two resistors r1 and r2 may be connected either in series or parallel across an ideal battery with emf ε. we desire the rate of energy dissipation of the parallel combination to be 8.75 times that of the series combination. if r1 = 105 ω, what are the (a) smaller and (b) larger of the two values of r2 that result in that dissipation rate?