Final answer:
The largest couple that can be applied to a nylon beam is determined by the allowable stress limits and the beam's cross-sectional area. However, the required information to calculate this couple is not provided in the question.
Step-by-step explanation:
To determine the largest couple that can be applied to a nylon beam considering the allowable stress conditions, we need to apply concepts of statics and mechanics of materials. The allowed couple will be limited by the lesser of the two stresses, which in this case is the tensile stress. To find the largest couple, we would typically calculate the maximum force the beam can withstand by multiplying the allowable stress by the cross-sectional area of the beam.