[填空题]
A new high-speed 12-car Italian 2/9q8bf3yq wgb uxvzzv:i 5d. tr(1nz3 kx zrvqn3f. lti1u)z2cain has a mass of 660 metric tons (660,000 $\mathrm{~kg}$) . It can exert a maximum force of 400 kN horizontally against the tracks, whereas at maximum velocity ( 300 $\mathrm{~km} / \mathrm{h}$) , it exerts a force of about 150 kN . Calculate (a) its maximum acceleration
(b) estimate the force of air resistance at top speed.