900 cm^3 * 8.15 g/ cm^3 = 7335 g for each part
7335 g * 1 kg/1000 g = 7.335 kg
each part weighs 7.335 kgs
they are buying 300 parts
300 * 7.335 kg = 2200.5 kg for the 300 parts
It cost $.37 per kg
2200.5 kg * $.37 per kg = $814.185 for the 300 parts
To the nearest dollar
$814