Answer:
B. double.
Step-by-step explanation:
At the Pareto optimal point, MPK/MPL = Price of K/Price of L
Substitute the given information as :
L/K = r/w or K/L = w/r
When r decreases by 50%,
L'/K' = 0.5r/w or K'/L '= 2w/r
From above, K'/L' = 2(K/L)
Thus, capital to labor ratio (K/L) will double as double of capital will now be used since its price has fallen by half.