Step 1 :Calculate the total number of orders: \(328 + 266 + 237 + 148 + 38 + 60 + 31 + 20 = 1128\)
Step 2 :Calculate the number of orders from Restaurant C: \(237 + 31 = 268\)
Step 3 :Calculate the number of orders that are not accurate: \(38 + 60 + 31 + 20 = 149\)
Step 4 :Calculate the probability of getting an order from Restaurant C: \(268 / 1128 = 0.238\)
Step 5 :Calculate the probability of getting an order that is not accurate: \(149 / 1128 = 0.132\)
Step 6 :Calculate the number of orders from Restaurant C that are not accurate: \(31\)
Step 7 :Calculate the probability of getting an order from Restaurant C that is not accurate: \(31 / 1128 = 0.027\)
Step 8 :Calculate the probability of getting an order from Restaurant C or an order that is not accurate: \(0.238 + 0.132 - 0.027 = 0.343\)
Step 9 :Final Answer: The probability of getting an order from Restaurant C or an order that is not accurate is \(\boxed{0.343}\)