Christopher has just returned to the united states from a trip to singapore and australia. he is looking over his records of the money he spent on his trip. the following list shows items and expenses christopher paid for before and during his trip, as well as whether the purchase took place in us dollars (us$), singapore dollars (s$), or australian dollars (au$).

item
cost
currency
camera
139.54
us$
ferry ticket
525.15
au$
passport
33.45
us$
guide book
62.99
s$
hat
42.74
s$
plane ticket
849.52
au$

when christopher was on his trip, the exchange rate for us dollars to singapore dollars was 1: 1.3914, and the exchange rate for singapore dollars to australian dollars was 1: 0.7786. how much did christopher spend in total, measured in us dollars? round all currency values to two decimal places.
a.
$1,517.89
b.
$1,526.19
c.
$1,809.35
d.
$2,776.72