Ten persons numbered `1, 2,.....,10` play a chess tournament, each player against every other player exactly one game. It is known that no game ends in a draw. If `w_1, w_2,..... , w_(10)` are the number of games won by players `1, 2,.....,10` respectively, and `l_1, l_2,............., l_(10)` are the number of games lost by the players `1, 2,.....,10` respectively, then a. `sumw_i=suml_i=45` b. `w_i+1_i=9` c. `sumw l_1^2=81+suml_1^2` d. `sumw_i^2=suml_i^2`