Used car dealerships generally have sales quotas that they strive to hit each month, quarter, and calendar year. Consequently, buying a used car toward the end of those periods presents a great opportunity to get a good deal on the car. The accompanying file includes monthly sales data for used cars (Cars) from 20142019.

Click here for the Excel Data File

Date	Cars
January/14	138
February/14	179
March/14	151
April/14	176
May/14	176
June/14	212
July/14	199
August/14	233
September/14	233
October/14	202
November/14	176
December/14	180
January/15	176
February/15	148
March/15	171
April/15	166
May/15	197
June/15	199
July/15	214
August/15	230
September/15	224
October/15	177
November/15	183
December/15	173
January/16	178
February/16	133
March/16	150
April/16	168
May/16	189
June/16	210
July/16	229
August/16	234
September/16	242
October/16	168
November/16	186
December/16	191
January/17	154
February/17	142
March/17	165
April/17	173
May/17	194
June/17	203
July/17	230
August/17	206
September/17	221
October/17	167
November/17	174
December/17	183
January/18	175
February/18	152
March/18	161
April/18	170
May/18	180
June/18	184
July/18	220
August/18	220
September/18	215
October/18	172
November/18	158
December/18	170
January/19	156
February/19	150
March/19	173
April/19	184
May/19	164
June/19	201
July/19	199
August/19	206
September/19	235
October/19	146
November/19	163
December/19	195

Estimate the linear regression models using seasonal dummy variables with and without the trend term. Which is the preferred model?

Use the preferred model to forecast used car sales in the first two months of 2020.

Note: Round coefficient estimates to at least 4 decimal places and final answers to 2 decimal places.