In a particular experiment at 300°C, [NO₂] drops from 0.0290 to 0.00865 m in 240 s. The rate of disappearance of NO₂ for this period is _______ₘ/s.
a) 1.5710⁻⁴
b) 4.2410⁻5
c) 8.4810⁻⁵
d) 1.1810⁴
e) 1.7010⁻⁴