I want to plot three line plots in one graph. On the x-axis I want to have the quarters i.e. Q1, Q2, Q3, and Q4. And, on the y-axis I want to show the average, minimum, and maximum "sales" for each quarter.

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input int date float(quarter sales)
13239 144  15.07396
13330 145  15.22263
13422 146   15.7636
13514 147  17.03415
13604 148  17.59395
13695 149  18.00279
13787 150  18.07942
13879 151  21.87692
13969 152  22.51151
14060 153  22.81462
14152 154  24.65873
14244 155  27.38165
14334 156  28.00771
14425 157  28.02526
14517 158  28.05533
14609 159  27.08693
14700 160  29.16289
14791 161  30.16414
14883 162  32.27179
14975 163  34.43443
15065 164  36.40239
15156 165  35.48289
15248 166  35.10188
15340 167  36.21612
15430 168  37.56783
15521 169  36.78747
15613 170  36.58957
15705 171  37.74507
15795 172  36.79951
15886 173  42.71779
15978 174  43.54155
16070 175   44.6773
16161 176  47.31126
16252 177  50.62463
16344 178  51.71962
16436 179  50.26723
16526 180  52.15678
16617 181  52.95755
16709 182  54.54217
16801 183  55.01907
16891 184  57.37235
16982 185  59.59472
17074 186  62.04618
17166 187  65.14246
17256 188    67.598
17347 189  69.60613
17439 190    70.948
17531 191  75.71963
17622 192  73.87219
17713 193  72.65429
17805 194   71.2222
17897 195  69.34279
17987 196  71.96011
18078 197  73.72668
18170 198  75.46033
18262 199  76.14115
18352 200  78.47517
18443 201  78.30347
18535 202  79.78409
18627 203  80.78126
18717 204  81.86597
18808 205  83.78559
18900 206   81.7859
18992 207  73.38277
19083 208  73.07322
19174 209  74.47658
19266 210  77.54887
19358 211  80.99576
19448 212  82.05329
19539 213   80.5828
19631 214  82.75167
19723 215  83.92115
19813 216  86.00323
19904 217  89.75872
19996 218  89.61819
20088 219  90.73944
20178 220   94.8772
20269 221  94.64499
20361 222  94.31632
20453 223  96.68026
20544 224  97.78695
20635 225  97.12594
20727 226  97.48424
20819 227  98.30496
20909 228 102.56005
21000 229 102.88103
21092 230 104.58755
21184 231 104.64616
21274 232 101.83655
21365 233  102.9994
21457 234  103.4964
21549 235  102.7439
end
format %tdnn/dd/CCYY date
format %tq quarter