SCED = CD x CE x 1/2 = AB x CE x 1/2 = 27 x 5 x 1/2 = 67,5 (cm2)
SDAM = AD x AM x 1/2 = 18 x 8 x 1/2 = 72 (cm2)
SNBE = NB x BE x 1/2 = (AB - AM - MN) x (BC - CE) x 1/2 = (AB - AM - MN) x (AD - CE) x 1/2 = (27 - 8 - 10) x (18 - 5) x 1/2 = 58,5 (cm2)
SABCD = AB x AD = 27 x 18 = 486 (cm2)
SMNED = SABCD - SNBE - SCED - SDAM = 486 - 58,5 - 67,5 - 72 = 288 (cm2)