If I have the following data (**I have updated the data**):

      data={{{60, 1852.94}, {65, 178.035}, {70, 7.97143}, {75, 48.9479}, {80, 
      133.561}, {85, 8.65079}, {87, 1.78915}}

How can I fit it to the following equation?

    eq = 1/((x*c1)/((Exp[B1/(x - T0)])^0.75)*(1 - Exp[((Tm - x)*c2)/Tm^2])) /. {T0 -> 259.246,B1 -> 2595.89, Tm -> 170 + 273.15}

I am trying the following:


      fun[x_] = NonlinearModelFit[data,eq, {c1, c2}, x] // Normal (*c1=1.07571*10^11, c2=1.67014*10^7*)

Which gives me an erroneous `c1` and `c2` of `c1=1.07571*10^11` & `c2=1.67014*10^7`. When I do it in excel it gives me a `c1` of 313634 and a `c2` of -8434.47 which fits the data relative well. Why mathematica is not fitting the data or finding the correct `c1` and `c2` values?