Q:   The binary system is 2.1 times brighter than the Sun.
             What is the absolute magnitude of the binary system?


           We know that the absolute magnitude of the Sun is +4.67,
           so the absolute magnitude of KIC 8736245 can be computed
           as follows:

                                                        I(KIC)
                M(KIC)  -  M(Sun)   =   -2.5 * log10 ( ------- )
                                                        I(Sun)

                                                       
                M(KIC)  -  M(Sun)   =   -2.5 * log10 (  2.1 )

                M(KIC)  -  M(Sun)   =   -0.81

                M(KIC)              =   M(Sun)  -  0.81

                                    =   4.67    -  0.81 

                                    =   3.86