If the labour market is perfectly competitive, labour demand function is given by ND $=$ a $+$ bW and labour supply function is given by NS $=$ c $+$ dW; W is the wage rate, and a$,$ b$,$ c$,$ and d are constants. At market equilibrium, we can determine the market wage rate as:

a$.$

$($a $+$ c$)/($d $+$ b$).$

b$.$

$($a $-$ c$)/($d $-$ b$).$

c$.$

$($a $+$ c$)/($d $-$ b$).$

d$.$

$($a $-$ c$)/($d $+$ b$).$

e$.$

$($d $+$ b$)/($a $+$ c$).$