I already have the answers, but I need the explanation

Q13: When tones that are very close together in frequency are sounded together, a beat pattern is produced which is perceived as an alternating loud/soft pulse. The frequency of this pulse is the difference in the frequencies of the two tones. This is one reason why it is important for musical instruments in an orchestra to be in tune. Suppose there are three tuning forks, A, B and C, and that fork B has a frequency of 440 Hz. When A and B are sounded together, a beat frequency (the frequency of the pulse) of 3 Hz is heard. When B and C are sounded together, the beat frequency is 4H2. (A) What are the possible frequencies of A? (2 points) 437 Hz (B) What are the possible frequencies ofC? (2 points) 443 Hz (C) What beat frequencies are possible when A and C are sounded together? (3 points) 436 Hz (D) Assume each fork produces a sound level 0175 dB. [fall three ofthe forks are sounded together. what is the new sound level? (3 points) 444HZ