A Tractor of Mass $M_{1}=2,000 \mathrm{~kg}$ Is Pulling a Trailer of Mass

Multiple Choice

A tractor of mass $M_{1}=2,000 \mathrm{~kg}$ is pulling a trailer of mass $M_{2}=5,000 \mathrm{~kg}$ . If the tractor-trailer is accelerated at $2.0 \mathrm{~m} / \mathrm{s}^{2}$ , and air resistance is negligible, then the magnitude of the force the tractor applies to the road is

A) $12,000 \mathrm{~N}$
B) $14,000 \mathrm{~N}$
C) $6,000 \mathrm{~N}$ .
D) $8,000 \mathrm{~N}$ .
E) $10,000 \mathrm{~N}$