Upon the filing of an application for assistance to the aged, blind, or disabled, the Department of Health and Human Services shall make such investigation as it deems necessary to determine the circumstances existing in each case. Each applicant and recipient shall be notified in writing as to (1) the approval or disapproval of any application, (2) the amount of payments awarded, (3) any change in the amount of payments awarded, and (4) the discontinuance of payments.