financial model

Maybe like this:

      --A-- --------------------------------B---------------------------------
  1   25000                                                                   
  2                                                                           
  3   12500 A3 =A$1 * LOOKUP(A$1, {0,25000,100000}, {1,0.5,0.333333333333333})
  4   12500 A4 =A$1 * LOOKUP(A$1, {0,25000,100000}, {0,0.5,0.333333333333333})
  5       0 A5 =A$1 * LOOKUP(A$1, {0,25000,100000}, {0,0,0.333333333333333})

Edit: cassandra, please take a few minutes to read the forum rules about thread titles before posting again.