given that a space craft is approaching too close to the sun. the temperature of craft at (x,y,z) is T(x,y,z)=exp(-x^2-2y^2-3Z^2)where x,y,z are in metres. the craft is now at (1,1,1). if the craft travels at exp(8) metres pre sec, how fast will the temperature decrease if it proceeds in that direction?

my working,

the craft will decrease the fastest in the direction of neg grad T. hence the rate of decrease would be the magnitude of grad T...however i didnt manage to get the answer...

can someone help me?

thanks.