“…If this statement is false, then there exists a pair of constants and such that Thus there is an integer such that Let and consider the -function as follows for a positive constant a . We note that is a nonnegative function verified from the fact that Then by the Dynkin formula [ 2 ], we obtain for all that where is given by Hence which implies that Choose such that , it yields where is the following positive number Substituting ( 10 ) into ( 9 ), we obtain Similar to the method developed in the study conducted by [ 1 , 9 ], we obtain which is a contradiction. So,we must have a.s. Consequently, s ( t ), u ( t ), q ( t ) and c ( t ) are positive and the solution of ( 2 ) is global.…”