A can of paint that covers 20 ? costs $24.60. The walls of a room 13 ft x 18 ft are 8 ft high.

What is the cost of paint for the walls?

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To a fish, the 4.20 mm thick aquarium walls appear to be only 3.80 mm thick, what is the index of refraction of the walls?

Suppose that the resistance between the walls of a biological cell is 3.22 x 109. (a) What is the current when the potential difference between the walls is 74.6 mV? (b) If the current is composed of Na+ ions (q = +e), how many such ions flow in 0.726 s?