In which year the total production of cars of types P and Q together was equal to the total production of cars of types R and S together?

From above given table , we can see that
from year 1989 to 1994 ,( P + Q ) :
In 1989 = 8 + 16 = 24 ,
In 1990 = 20 + 10 = 30 ,
In 1991 = 16 + 14 = 30 ,
In 1992 = 17 + 12 = 29 ,
In 1993 = 21 + 12 = 33 ,
In 1994 = 6 + 14 = 20
simillary , ( R + S ) :
In 1989 = 21 + 4 = 25 ,
In 1990 = 17 + 6 = 23 ,
In 1991 = 16 + 10 = 26 ,
In 1992 = 15 + 16 = 31 ,
In 1993 = 13 + 20 = 33 ,
In 1994 = 8 + 31 = 39
Hence, In 1993 year , the total production of cars of types P and Q together will be equal to the total production of cars of types R and S together