$\backslash$table$[[6,($a$)$ Explain the following terminologies of a straight tooth spur gear$]]$

drive with a neat sketch:

$($i$)$ Addendum circle

$($ii$)$ Pitch circle diameter

$($iii$)$ Pressure angle

$($b$)$ The number of teeth in a spur gear is $28.$ The gear has a module

of $2$ mm and it rotates at $250$ r$.$p$.$m$.$ Calculate its circular pitch and

pitch line velocity