$[$Maximum mark:$6]$

$($a$)$ Describe the quark structure of a baryon.

$($b$)$ The Feymman diagram shows a possible decay of the $K^{+}$meson.

Idently the interactions that are involved at points A and B in this decay.

$($c$)$ The $K^{+}$meson candecay as

$K^{+}{}^{+}+v_w$

State and explain the interacton that is responsible for this decay