JATER

假設原本有$10, 用$8買雞, 剩$29 o4 J2 H; c' N$ Z; e6 D5 P
之後$9賣出, $2+$9 = $11tvb now,tvbnow,bttvb2 q5 L. ~$ ~5 V, I- i* ^
再用$10買雞, $11-$10 = $1" I7 K. ^  h; o+ t, N) B
又再以$11賣出, $1+$11 = $12
  a$ \6 S$ r- z$ ^8 |& [+ s3 n- B, Y: @$12-$10 = 賺$2