Answer
$m_{lead}=6693.75\frac{kg}{year}$
Work Step by Step
The amount of lead put into the atmosphere per year in that city will be:
$m_{lead}=0.5*70000car*15000\frac{km}{car,year}*\frac{8.5L}{100km}*0.15\frac{g}{L}$
$m_{lead}=6693.75\frac{kg}{year}$
