Molecular weight of pbcl2 = 278 g/mole mass of beaker + pbcl2 = 62.19 g mass of beaker = 57.77 g mass of pbcl2 per 100 ml = g moles pbcl2 per 100 ml = [pb-2] based upon this investigation = m [cl-] based upon this investigation = m

PbCl2--->Pb2+  +  2Cl-

The  mass   of  PbCl2   is   =mass   of  the  beaker+Pbcl2  minus   mass  of  the  beaker
that  is  62.19-57.77g=  4.42grams

moles  of PbCl2=  4.42g/278g/m0l = 0.0159moles

concentration  of  (Pb2+)
since  mole  ratio  of  PbCl2  to  Pb2+  is   1:1  therefore  the  moles  of  Pb2+  is  also  0.0159moles
concentration  =0.0159/100 x1000=0.159M

concentration  of  CI-  is  two  time  that  of  Pb2+  from  the  equation  above  therefore  concentration   of  Cl-  =  0.159 x2  =0.318M

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.