Seriously, watch the videos from past inaugurations. 4 cannons, at the Capitol, short (3 second interval) between each shot, for the 21 gun salute:
Trump: https://www.youtube.com/watch?v=sN1zIJc8PUU
Obama: https://www.c-span.org/video/?310517-1/57th-presidential-inauguration-ceremony-compilation [beginning 1:43:55]
Clinton: https://youtu.be/0Cyu_3OiecY?t=3535 [beginning 58:55]
Reagan: https://youtu.be/XXtJ0uW10Ug?t=80 [beginning 1:20]
Biden:
3 cannons
at Arlington Cemetery, not the Capitol
at least 5 second interval between shots
https://youtu.be/FognBPhs5rw?t=31103 [beginning 8:38:23]
Here is a link to Army Regulation AR 600-25, which details "salutes":
https://armypubs.army.mil/epubs/DR_pubs/DR_a/pdf/web/ARN20654_R600_25_Admin_FINAL.pdf
🤔