A possibility of running first: b= 1*5*4*3=60.
B the possibility of running fourth: c=5*4*3* 1=60.
Possibility of A running B first: d =1* 4 * 3 *1=12.
The possibility of A not running first and B not running fourth y = a-b-c+d = 360-60-60+12 = 252.
Possibility of running seconds: e=5* 1*4*3=60.
Possibility of A running second and B running fourth: f = 4 *1* 3 *1=12.
Possibility of A running second and B not running fourth: x=60- 12=48.
The probability of A running second: s=x/y=48/252= 19.05%.