Answer
(a) $85.2Kg\cdot m/s$
(b) $108000Kg \cdot Km/h$
Work Step by Step
(a) We know that the linear momentum can be calculated as follows:
$p=mv$
We plug in the known values to obtain:
$p=7.1\times 12=85.2Kg\cdot m/s$
(b) We know that
$p=mv$
We plug in the known values to obtain:
$p=1200\times 90=108000Kg \cdot Km/h$