Solve the problem.A construction crane lifts a 100-lb bucket originally containing 140 lb of sand at a constant rate. The sand leaks out at a constant rate so that there is only 70 lb of sand left when the crane reaches a height of 90 feet. How much work is done by the crane?
A. 3375 ft ? lb
B. 18,450 ft ? lb
C. 21,600 ft ? lb
D. 9450 ft ? lb
Answer: B
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The position vector of a particle is r(t). Find the requested vector.The velocity at t = 4 for r(t) = (3t2 + 4t + 7)i - 4t3j + (8 - t2)k
A. v(4) = 28i + 192j + 8k B. v(4) = 16i - 64j - 4k C. v(4) = 20i - 192j - 8k D. v(4) = 28i - 192j - 8k
Solve the problem.Suppose the government wants to impose a tax on fossil fuels to reduce carbon emissions. The cost benefit is modeled by 
where x represents the dollars of tax per ton of carbon emitted and P represents the percent reduction in emissions of carbon. (P is in decimal form.) Determine P when 
Round to three decimal places.
A. -0.190 B. 1.806 C. -0.11 D. 0.194
Find the indicated term of the arithmetic sequence.5.9, 5.6, 5.3, . . . ; a9
A. 3.51 B. 3.2 C. 3.5 D. 3.8
Factor completely. If prime, so indicate.10z2 - 11z - 6
A. prime B. (2z + 3)(5z - 2) C. (10z - 3)(z + 2) D. (2z - 3)(5z + 2)