Answer:
= 3916624286969936

Explanation:
1 kg = 1000 gr
7.8kg = 7.8*1000 = 7800 gr
1m = 3.281 ft
(1m)² = (3.281ft)² = 10.765ft²
1 hora = 3600 seg
1 seg = 1/3600 = 0.0002778 horas
(1 seg)³ = (0.0002778horas)³ = 0.0000000000214335horas³
Entonces:
7.8kg m²/seg³ = 7800g * 10.765ft / 2.14335*10⁻¹¹
= 3916624286969936 (gr ft²)/hora³
= 3.916 * 10¹⁵