A summer youth employment program has 1390 participants. As part of the data analysis of the program, a pre-employment survey and a post-employement survey was sent to each participant. Suppose 500 responded to the pre-employment survey, 410 responded to the post-employment survey, and 375 responded to both. How many participants responded to at least one of the surveys? Store you answer in the variable num_responded.

num_responded = None# YOUR CODE HEREraise NotImplementedError()