Q:  What is the logarithmic slope on this graph?


         At the bottom left,

             M  =   10^(11)          log(M) = 11.0
             r  =    8               log(r) =  0.90

         At the top right,

             M  =    1.5 x 10^(12)   log(M) = 12.18
             r  =  300               log(r) =  2.48


       So  
                         12.18 - 11.00
             slope  =   ----------------   =  0.75
                          2.48 -  0.90