(a) Executors and administrators shall be allowed such compensation for their services as the court considers just, except that, when the deceased by his will, has made special provision for the compensation of his executor, such executor is not entitled to any other compensation for his services unless he shall within ten days after his appointment subscribe and file with the court a written declaration renouncing the compensation provided by the will.
(b) Notwithstanding a provision in the will for the compensation of an executor, if the estate is insufficient to satisfy the claims against it, the court shall reduce such compensation, so far as may be necessary to satisfy such claims, to an amount equal to that which the executor would have been entitled to if no such provision had been made.