$[$CO$3]$: For a $10$ element array of isotropic antennas with equal spacing of $0\mathrm{.}6$ and fed

with equal amplitude and phase, Determine:

$($a$)$ Approximate gain of the array in dBi, assuming $90\%$ efficiency,

$($b$)$ Approximate HPBW of the array

$($c$)$ Approximate direction of first null from broadside

$($d$)$ The direction of first side lobe level from broadside