{f=D[((130*(k-340)/3300+1000)/1000)*(1+((200*(l-380)/3300+50)/1000)*((200*(l-380)/3300+400)/1000))*(1+0.25*(550*(m-380)/3300/1000))*(1/(1-130*(n-380)/3300/1000)),k],k=1723,l=1545,m=2660,n=2322}