A nasa spacecraft measures the rate r of at which atmospheric pressure on mars decreases with altitude. the result at a certain altitude is: = r0.0421·kpakm-1 convert r to ·jcm-4.

this is simple question of conversion of unit But as we can see here that one is in kpa or kilo pascal which is a unit of pressure while another is in joule which is unit of energy but if we do the dimension matching we could see that 1pa = 1J/m^3 and 0.0421kpa/km=0.0421pa/m now putting above equation as substitution 0.0421pa/m=0.0421J/m^4 100 cm = 1 m putting it we get R = 4.21Ă-10^-10 J/cm^4