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Simplify 15(x - 4)(x -1)-3(x + 4)(x - 1) with steps

The pyramid below was dissected by a horizontal plane which shape describes the pyramid horizontal cross section

Which of the following would be a reasonable estimate for the weight of a pencil? a. 1 × 10^-20 lb b. 1 × 10^20 lb c. 1 × 10^2 lb d. 1 × 10^-2 lb