Answer
$$K = 6.9 \times 10^{-4}$$
Work Step by Step
1. The exponent of each concentration is equal to its balance coefficient.
$$K = \frac{[Products]}{[Reactants]} = \frac{[ NO ] ^{ 2 }}{[ N_2 ][ O_2 ]}$$
2. Substitute the values and calculate the constant value:
$$K = \frac{( 4.7 \times 10^{-4} )^{ 2 }}{( 0.041 )( 0.0078 )} = 6.9 \times 10^{-4}$$