Plane intersect with X axis with intercept a and plane is parallel to y axis , hence y intercept is infinity

z intercept is 1/2 a

now intercepts are ( a, infinity , 1/2a) , we take a out , hence fractional intercepts = ( 1,1/infinty , 1/2)

now we take reciprocal , ( 1/ , 1/ infinity , 1/1/2) = (1,0,2)

Hence Milelr indices ( 102)