A preparation of 40 mg/L solution of toluene is prepared by adding 4.6 micrograms of toluene to 100.0mL of distilled water. Explain how many mL of this original solution are required to prepare 10mL solution of a 20 mg/L and then from the 20 mg/L define how many mL are required to make 10mL of 4 mg/L?