A out of 10 trials, a receiver got four cards correct. what is her success rate? what is her expected rate of success, assuming she is only guessing?

Complete question:

One classical experiment on ESP (extrasensory perception) tests for telepathy between two participants by using five cards with different designs, all known to both participants. For each trial, the "sender" participant sees a randomly chosen card and concentrates on its design. The "receiver" attempts to guess the identity of the card. Assume that each of the five cards is equally likely to be chosen.

Out of 10 trials, a receiver got four cards correct. What is her success rate? What is her expected rate of success, assuming she is only guessing?

answer:

Success rate = 4/10 = 40%

Expected success rate = 1 out of 5 correct = 20%