Answer:
10√7 pound
Explanation:
R = √A² + B² + 2ABcos∅
=> 40 = √30² + B² + 2ABcos0°
=> 40² = 30² + B² + 0
=> 1600 - 900 = B²
=> √700 = B
=> 10√7 = B
Note that if R = 50*, B = 40 pounds
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